This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:                3GPP third generation partnership project        ACK acknowledge        BW bandwidth        CC component carrier        CCE control channel element        CDM code division multiplexing        CoMP coordinated multi-point        DCI downlink control information        DL downlink (eNB towards UE)        eNB E-UTRAN Node B (evolved Node B)        EPC evolved packet core        E-UTRAN evolved UTRAN (LTE)        ePDCCH enhance PDCCH        HARQ hybrid automatic repeat request        IMT-A international mobile telephony-advanced        ITU international telecommunication union        ITU-R ITU radiocommunication sector        LTE long term evolution of UTRAN (E-UTRAN)        MAC medium access control (layer 2, L2)        MM/MME mobility management/mobility management entity        NACK negative-acknowledge        Node B base station        O&M operations and maintenance        OFDMA orthogonal frequency division multiple access        PDCCH physical downlink control channel        PDCP packet data convergence protocol        PDSCH physical downlink shared channel        PHY physical (layer 1, L1)        PUCCH physical uplink control channel        PUSCH physical uplink shared channel        RLC radio link control        RRC radio resource control        RRH remote radio head        RRM radio resource management        SC-FDMA single carrier, frequency division multiple access        S-GW serving gateway        UE user equipment, such as a mobile station or mobile terminal        UL uplink (UE towards eNB)        UTRAN universal terrestrial radio access network        
The specification of a communication system known as evolved UTRAN (E-UTRAN, also referred to as UTRAN-LTE or as E-UTRA) is currently nearing completion within the 3GPP. As specified the DL access technique is OFDMA, and the UL access technique is SC-FDMA.
One specification of interest is 3GPP TS 36.300, V8.12.0 (2010-04), “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E UTRA) and Evolved Universal Terrestrial Access Network (E UTRAN); Overall description; Stage 2 (Release 8)”. This system may be referred to for convenience as LTE Rel-8 (which also contains 3G HSPA and its improvements). In general, the set of specifications given generally as 3GPP TS 36.xyz (e.g., 36.211, 36.311, 36.312, etc.) may be seen as describing the Release 8 LTE system. More recently, Release 9 versions of at least some of these specifications have been published including 3GPP TS 36.300, V9.9.0 (2011-12), and Release 10 versions of at least some of these specifications have been published including 3GPP TS 36.300, V10.6.0 (2011-12). Even more recently, Release 11 versions of at least some of these specifications have been published including 3GPP TS 36.300, V11.0.0 (2011-12).
FIG. 1 reproduces FIG. 4-1 of 3GPP TS 36.300, and shows the overall architecture of the E-UTRAN system. The E-UTRAN system includes eNBs, providing the E-UTRA user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE (not shown). The eNBs are interconnected with each other by means of an X2 interface. The eNBs are also connected by means of an S1 interface to an EPC, more specifically to a MME (Mobility Management Entity) by means of a S1 MME interface and to a Serving Gateway (SGW) by means of a S1 interface. The S1 interface supports a many-to-many relationship between MMEs/S-GW and eNBs.
The eNB hosts the following functions:                functions for RRM: Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both UL and DL (scheduling);        IP header compression and encryption of the user data stream;        selection of a MME at UE attachment;        routing of User Plane data towards the Serving Gateway;        scheduling and transmission of paging messages (originated from the MME);        scheduling and transmission of broadcast information (originated from the MME or O&M); and        a measurement and measurement reporting configuration for mobility and scheduling.        
Of particular interest herein are the further releases of 3GPP LTE (e.g., LTE Rel-10) targeted towards future IMT-A systems, referred to herein for convenience simply as LTE-Advanced (LTE-A). Reference in this regard may be made to 3GPP TR 36.913, V8.0.1 (2009 03), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Requirements for Further Advancements for E UTRA (LTE-Advanced) (Release 8). A goal of LTE-A is to provide significantly enhanced services by means of higher data rates and lower latency with reduced cost. LTE-A is directed toward extending and optimizing the 3GPP LTE Rel-8 radio access technologies to provide higher data rates at very low cost. LTE-A will most likely be part of LTE Rel-10. LTE-A will be a more optimized radio system fulfilling the ITU-R requirements for IMT-A while maintaining backward compatibility with LTE Rel-8. Reference is further made to a Release 9 version of 3GPP TR 36.913, V9.0.0 (2009-12). Reference is also made to a Release 10 version of 3GPP TR 36.913, V10.0.0 (2011-06).
As is specified in 3GPP TR 36.913, LTE-A should operate in spectrum allocations of different sizes, including wider spectrum allocations than those of Rel-8 LTE (e.g., up to 100 MHz) to achieve the peak data rate of 100 Mbit/s for high mobility and 1 Gbit/s for low mobility. It has been agreed that carrier aggregation is to be considered for LTE-A in order to support bandwidths larger than 20 MHz. Carrier aggregation, where two or more component carriers (CCs) are aggregated, is considered for LTE-A in order to support transmission bandwidths larger than 20 MHz. The carrier aggregation could be contiguous or non-contiguous. This technique, as a bandwidth extension, can provide significant gains in terms of peak data rate and cell throughput as compared to non-aggregated operation as in LTE Rel-8.
A terminal may simultaneously receive one or multiple component carriers depending on its capabilities. A LTE-A terminal with reception capability beyond 20 MHz can simultaneously receive transmissions on multiple component carriers. A LTE Rel-8 terminal can receive transmissions on a single component carrier only, provided that the structure of the component carrier follows the Rel-8 specifications. Moreover, it is required that LTE-A should be backwards compatible with Rel-8 LTE in the sense that a Rel-8 LTE terminal should be operable in the LTE-A system, and that a LTE-A terminal should be operable in a Rel-8 LTE system.
FIG. 2 shows an example of the carrier aggregation, where M Rel-8 component carriers are combined together to form M×Rel-8 BW (e.g., 5×20 MHz=100 MHz given M=5). Rel-8 terminals receive/transmit on one component carrier, whereas LTE-A terminals may receive/transmit on multiple component carriers simultaneously to achieve higher (wider) bandwidths.
With further regard to carrier aggregation, what is implied is that one eNB can effectively contain more than one cell on more than one CC (frequency carrier), and the eNB can utilize one (as in E-UTRAN Rel-8) or more cells (in an aggregated manner) when assigning resources and scheduling the UE.
Coordinated multi-point (CoMP) offers higher data transmission rate and better quality. These benefits may be seen especially for cell-edge users. In one CoMP scenario (scenario #3), inter-cell coordination operations occur where the remote radio heads (RRHs) and the eNB have different cell IDs.
In order to improve reception performance and reduce UE's uplink transmit power, a UE's reception points could be selected based on which reception has the better receive power at the reception point. In the downlink, the power received at a UE from a transmission point may also depend on the transmit power of that transmission point in addition to the path loss between the UE and the transmission point. For heterogeneous networks when transmitters of different power classes are used, the best transmission point may not correspond to the best reception point. The transmission point and the reception point may use different CC. The signal response in the CC may also influence which transmission point and/or reception point is preferred.
FIG. 3 illustrates PUCCH transmissions in a CoMP scenario. This scenario is often referred to as “Scenario #3”. As shown, the macro-cell 310 is served by eNB1. The macro cell 310 includes micro cells 320 and 330. Micro-cell 320 is served by RRH1 and micro-cell 330 is served by remote radio head (RRH) RRH2. As shown, RRH1 and RRH2 can communicate with eNB1 over the backhaul (e.g., a fiber cable).
In CoMP scenario 3, UEs can roughly be divided into three categories: RRH UEs which have RRH as reception and transmission point; CoMP UEs which have an eNB as transmission point (e.g., for PDCCH) and a RRH as reception point (e.g., for PUCCH/PUSCH); and legacy mode UEs which have eNB as both the reception and transmission point. The various UEs in FIG. 3 are shown operating in the macro-cell. As shown, eNB1 is the optimal transmission point for UE1 while RRH1 is the optimal reception point. Therefore, UE1 is operated as a CoMP UE in order to use the eNB1 as a transmission point and the RRH1 as a reception point. UE2 and UE3 are both RRH UEs. UE2 uses RRH1 as both a transmission point and as a reception point. Likewise, UE3 uses RRH2. Lastly, UE5 operates in a legacy mode using eNB1 as both a transmission point and as a reception point.
The general PUCCH resource determination for HARQ-ACK feedback in Rel 8/9/10, as stated in 3GPP TR 36.213 v.10.4.0, specifies: “for a PDSCH transmission indicated by the detection of a corresponding PDCCH in subframe n-4, or for a PDCCH indicating downlink SPS release (defined in section 9.2) in subframe n-4, the UE shall use nPUCCH(1,p=p0)=nCCE+NPUCCH(1) for antenna port p0, where nCCE is the number of the first CCE (i.e. lowest CCE index used to construct the PDCCH) used for transmission of the corresponding DCI assignment and NPUCCH(1) is configured by higher layers” (10.1.2.1).
Accordingly, the PUCCH index of a UE is determined by a dynamic PUCCH starting point NPUCCH(1) and the first CCE index nCCE of the corresponding DCI assignment, where the NPUCCH(1) is configured through high layer signaling (e.g., by a downlink serving basestation). This in turn influences which physical uplink control channel (PUCCH) will be used. As shown in FIG. 3, NPUCCH(1) of the UE1 is configured by higher signaling from the eNB1 and NPUCCH(1) of the UE2 is configured by higher signaling from the eNB2.
With the flexible uplink access (where reception points are selected independently of transmission points), the targeted reception cell may be different from the cell that granted the uplink transmission. Because nCCE is randomly determined by the PDCCH CCE mapping and the NPUCCH(1) or is configured by the UE's DL serving cell, it is possible that the PUCCH resource nPUCCH(1,p=p0)=nCCE+NPUCCH(1) used by a CoMP UE may collide with a PUCCH resource of a RRH UE which has the same RRH as an uplink reception point.
Conventional techniques have attempted to solve the PUCCH collision issue. A first technique reserves an additional dynamic PUCCH region for eNB on each RRH and introduces a UE-specific PUCCH dynamic resource offset parameter. With the help of a PUCCH resource offset parameter, the dynamic PUCCH region on RRH1 for CoMP UE is moved to avoid collision with the one on eNB1. Another technique reserves a feedback resource on the uplink of the targeted reception cell if the targeted transmission cell and targeted reception cell of a UE are different. The parameter(s) related with the feedback resource are indicated to the UE. A third approach shares orthogonal/non-orthogonal PUCCH resources to improve baseline CoMP operation. This operates by having multiple PUCCH resource pools for CoMP which can be implemented by decoupling the cell ID used for PDCCH and PUCCH.
These three approaches focus on providing different PUCCH resources nPUCCH(1,p=p0)=nCCE+NPUCCH(1) for RRH UE and CoMP UE by providing different NPUCCH(1). However, these techniques may increase the overhead in the PUCCH, for example, by reserving various PUCCH areas which might otherwise be used.
What is needed is a technique to prevent PUCCH collision between RRH UEs and CoMP UEs when both share the same RRH as uplink reception point.